The fate of a polygenic phenotype within the genomic landscapes of introgression in the European seabass hybrid zone

Unraveling the evolutionary mechanisms and consequences of hybridization is a major concern in biology. Many studies have documented the interplay between recombination and selection in modulating the genomic landscape of introgression, but few have considered how associations with phenotype may affect this landscape. Here, we use the European seabass (Dicentrarchus labrax), a key species in marine aquaculture that undergoes natural hybridization, to determine how selection on phenotype modulates the introgression landscape between Atlantic and Mediterranean lineages. We use a high-density SNP array to assess individual local ancestry along the genome and improve the mapping of muscle fat content, a polygenic trait that is divergent between lineages. Taking into account variation in recombination rates, we reveal a purging of Atlantic ancestry in the admixed Mediterranean populations. While Atlantic individuals had higher muscle fat content, we observed that genomic regions associated with this trait also displayed reduced introgression of Atlantic ancestry. These results emphasize how selection against maladapted alleles shape the genomic landscape of introgression.

解析杂交的演化机制与演化后果，是生物学领域的核心研究议题之一。诸多研究已证实重组与选择的相互作用可调控渐渗（introgression）的基因组格局，但鲜有研究探讨表型关联如何影响这一格局。本研究以自然发生杂交的海水养殖关键物种欧洲海鲈（Dicentrarchus labrax）为研究对象，旨在解析表型选择如何调控大西洋与地中海支系间的渐渗格局。本研究采用高密度SNP芯片评估个体基因组的局部祖先成分，并优化了肌肉脂肪含量的定位分析——该性状为多基因性状，且在两支系间存在显著分化。在考虑重组率变异的前提下，本研究揭示了混杂地中海种群中大西洋祖先成分的清除现象。尽管大西洋个体的肌肉脂肪含量更高，但本研究发现与该性状相关的基因组区域同样呈现出大西洋祖先成分渐渗水平降低的特征。上述结果阐明了针对不适应等位基因的选择如何塑造渐渗的基因组格局。